diff --git a/OpenRA.Game/Actor.cs b/OpenRA.Game/Actor.cs
index 1308ba32ef..717221cb3b 100755
--- a/OpenRA.Game/Actor.cs
+++ b/OpenRA.Game/Actor.cs
@@ -38,8 +38,7 @@ namespace OpenRA
 		public readonly World World;
 		public readonly uint ActorID;
 
-		[Sync]
-		public int2 Location;
+		public int2 Location { get { return traits.Get<IOccupySpace>().TopLeft; } }
 		[Sync]
 		public Player Owner;
 		[Sync]
@@ -52,11 +51,9 @@ namespace OpenRA
 		{
 			World = world;
 			ActorID = world.NextAID();
-			Location = location;
-			CenterLocation = Traits.Util.CenterOfCell(Location);
 			Owner = owner;
 
-			var init = new ActorInitializer( this );
+			var init = new ActorInitializer( this, location );
 
 			if (name != null)
 			{
@@ -70,6 +67,9 @@ namespace OpenRA
 					traits.Add(trait.Create(init));
 			}
 
+			if( CenterLocation == float2.Zero && traits.Contains<IOccupySpace>() )
+				CenterLocation = Traits.Util.CenterOfCell(Location);
+
 			Size = Lazy.New(() =>
 			{
 				var si = Info.Traits.GetOrDefault<SelectableInfo>();
@@ -262,10 +262,12 @@ namespace OpenRA
 	{
 		public readonly Actor self;
 		public World world { get { return self.World; } }
+		public readonly int2 location;
 
-		public ActorInitializer( Actor actor )
+		public ActorInitializer( Actor actor, int2 location )
 		{
 			this.self = actor;
+			this.location = location;
 		}
 	}
 }
diff --git a/OpenRA.Game/OpenRA.Game.csproj b/OpenRA.Game/OpenRA.Game.csproj
index 5f95edb4db..67a316fd7d 100755
--- a/OpenRA.Game/OpenRA.Game.csproj
+++ b/OpenRA.Game/OpenRA.Game.csproj
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003" ToolsVersion="3.5">
   <PropertyGroup>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
diff --git a/OpenRA.Game/Traits/Building.cs b/OpenRA.Game/Traits/Building.cs
index 31ac388e9c..d402dc0e84 100644
--- a/OpenRA.Game/Traits/Building.cs
+++ b/OpenRA.Game/Traits/Building.cs
@@ -54,14 +54,16 @@ namespace OpenRA.Traits
 		public readonly string DamagedSound = "kaboom1.aud";
 		public readonly string DestroyedSound = "kaboom22.aud";
 
-		public object Create(ActorInitializer init) { return new Building(init.self); }
+		public object Create(ActorInitializer init) { return new Building(init); }
 	}
 
-	public class Building : INotifyDamage, IResolveOrder, ITick, IRenderModifier
+	public class Building : INotifyDamage, IResolveOrder, ITick, IRenderModifier, IOccupySpace
 	{
 		readonly Actor self;
 		public readonly BuildingInfo Info;
 		[Sync]
+		readonly int2 topLeft;
+		[Sync]
 		bool isRepairing = false;
 
 		public bool Disabled
@@ -69,12 +71,13 @@ namespace OpenRA.Traits
 			get	{ return self.traits.WithInterface<IDisable>().Any(t => t.Disabled); }
 		}
 
-		public Building(Actor self)
+		public Building(ActorInitializer init)
 		{
-			this.self = self;
+			this.self = init.self;
+			this.topLeft = init.location;
 			Info = self.Info.Traits.Get<BuildingInfo>();
 			self.CenterLocation = Game.CellSize 
-				* ((float2)self.Location + .5f * (float2)Info.Dimensions);
+				* ((float2)topLeft + .5f * (float2)Info.Dimensions);
 		}
 		
 		public int GetPowerUsage()
@@ -157,5 +160,15 @@ namespace OpenRA.Traits
 					yield return a.WithPalette("disabled");
 			}
 		}
+
+		public int2 TopLeft
+		{
+			get { return topLeft; }
+		}
+
+		public IEnumerable<int2> OccupiedCells()
+		{
+			return Footprint.UnpathableTiles( self.Info.Name, Info, TopLeft );
+		}
 	}
 }
diff --git a/OpenRA.Game/Traits/Mobile.cs b/OpenRA.Game/Traits/Mobile.cs
index c70b5187d2..dc81a695b1 100644
--- a/OpenRA.Game/Traits/Mobile.cs
+++ b/OpenRA.Game/Traits/Mobile.cs
@@ -24,13 +24,13 @@ using OpenRA.GameRules;
 
 namespace OpenRA.Traits
 {
-	public class MobileInfo : ITraitInfo, ITraitPrerequisite<Unit>
+	public class MobileInfo : ITraitInfo, ITraitPrerequisite<UnitInfo>
 	{
 		public readonly UnitMovementType MovementType = UnitMovementType.Wheel;
 		public readonly int WaitAverage = 60;
 		public readonly int WaitSpread = 20;
 
-		public object Create(ActorInitializer init) { return new Mobile(init.self); }
+		public object Create(ActorInitializer init) { return new Mobile(init); }
 	}
 
 	public class Mobile : IIssueOrder, IResolveOrder, IOccupySpace, IMovement
@@ -38,36 +38,37 @@ namespace OpenRA.Traits
 		readonly Actor self;
 
 		[Sync]
-		int2 __fromCell;
+		int2 __fromCell, __toCell;
 		public int2 fromCell
 		{
 			get { return __fromCell; }
-			set { self.World.WorldActor.traits.Get<UnitInfluence>().Remove(self, this); __fromCell = value; self.World.WorldActor.traits.Get<UnitInfluence>().Add(self, this); }
+			set { SetLocation( value, __toCell ); }
 		}
+		[Sync]
 		public int2 toCell
 		{
-			get { return self.Location; }
-			set
-			{
-				if (self.Location != value)
-				{
-					self.World.WorldActor.traits.Get<UnitInfluence>().Remove(self, this);
-					self.Location = value;
-				}
-				self.World.WorldActor.traits.Get<UnitInfluence>().Add(self, this);
-			}
+			get { return __toCell; }
+			set { SetLocation( __fromCell, value ); }
+		}
+		void SetLocation( int2 from, int2 to )
+		{
+			if( fromCell == from && toCell == to ) return;
+			self.World.WorldActor.traits.Get<UnitInfluence>().Remove(self, this);
+			__fromCell = from;
+			__toCell = to;
+			self.World.WorldActor.traits.Get<UnitInfluence>().Add(self, this);
 		}
 
-		public Mobile(Actor self)
+		public Mobile(ActorInitializer init)
 		{
-			this.self = self;
-			__fromCell = toCell;
+			this.self = init.self;
+			this.__fromCell = this.__toCell = init.location;
 			self.World.WorldActor.traits.Get<UnitInfluence>().Add(self, this);
 		}
 
 		public void TeleportTo(Actor self, int2 xy)
 		{
-			fromCell = toCell = xy;
+			SetLocation( xy, xy );
 			self.CenterLocation = Util.CenterOfCell(fromCell);
 		}
 
@@ -102,6 +103,8 @@ namespace OpenRA.Traits
 			}
 		}
 
+		public int2 TopLeft { get { return toCell; } }
+
 		public IEnumerable<int2> OccupiedCells()
 		{
 			return (fromCell == toCell)
diff --git a/OpenRA.Game/Traits/TraitsInterfaces.cs b/OpenRA.Game/Traits/TraitsInterfaces.cs
index ea32ed9d32..7391301c9e 100644
--- a/OpenRA.Game/Traits/TraitsInterfaces.cs
+++ b/OpenRA.Game/Traits/TraitsInterfaces.cs
@@ -61,8 +61,32 @@ namespace OpenRA.Traits
 	}
 
 	public interface IDisable { bool Disabled { get; } }
-	
-	public interface IOccupySpace { IEnumerable<int2> OccupiedCells(); }
+
+	public interface IOccupySpace
+	{
+		int2 TopLeft { get; }
+		IEnumerable<int2> OccupiedCells();
+	}
+
+	public static class IOccupySpaceExts
+	{
+		public static int2 NearestCellTo( this IOccupySpace ios, int2 other )
+		{
+			var nearest = ios.TopLeft;
+			var nearestDistance = int.MaxValue;
+			foreach( var cell in ios.OccupiedCells() )
+			{
+				var dist = ( other - cell ).LengthSquared;
+				if( dist < nearestDistance )
+				{
+					nearest = cell;
+					nearestDistance = dist;
+				}
+			}
+			return nearest;
+		}
+	}
+
 	public interface INotifyAttack { void Attacking(Actor self); }
 	public interface IRenderModifier { IEnumerable<Renderable> ModifyRender(Actor self, IEnumerable<Renderable> r); }
 	public interface IDamageModifier { float GetDamageModifier( WarheadInfo warhead ); }
@@ -112,7 +136,7 @@ namespace OpenRA.Traits
 
 	public class TraitInfo<T> : ITraitInfo where T : new() { public virtual object Create(ActorInitializer init) { return new T(); } }
 
-	public interface ITraitPrerequisite<T> { }
+	public interface ITraitPrerequisite<T> where T : ITraitInfo { }
 
 	public interface INotifySelection { void SelectionChanged(); }
 	public interface ILoadWorldHook { void WorldLoaded(World w); }
diff --git a/OpenRA.Mods.Cnc/TiberiumRefineryDockAction.cs b/OpenRA.Mods.Cnc/TiberiumRefineryDockAction.cs
index e5f25f0787..4af4dfcc47 100644
--- a/OpenRA.Mods.Cnc/TiberiumRefineryDockAction.cs
+++ b/OpenRA.Mods.Cnc/TiberiumRefineryDockAction.cs
@@ -30,7 +30,7 @@ namespace OpenRA.Mods.Cnc
 {
 	class TiberiumRefineryDockActionInfo : TraitInfo<TiberiumRefineryDockAction> {}
 
-	class TiberiumRefineryDockAction : IAcceptOreDockAction, INotifyDamage, INotifySold, INotifyCapture, ITraitPrerequisite<IAcceptOre>
+	class TiberiumRefineryDockAction : IAcceptOreDockAction, INotifyDamage, INotifySold, INotifyCapture
 	{
 		Actor dockedHarv = null;
 		bool preventDock = false;
diff --git a/OpenRA.Mods.RA/Activities/Fly.cs b/OpenRA.Mods.RA/Activities/Fly.cs
index e5aa0ee84d..3359a1db49 100644
--- a/OpenRA.Mods.RA/Activities/Fly.cs
+++ b/OpenRA.Mods.RA/Activities/Fly.cs
@@ -68,9 +68,10 @@ namespace OpenRA.Mods.RA.Activities
 			var unit = self.traits.Get<Unit>();
 			var speed = .2f * Util.GetEffectiveSpeed(self, UnitMovementType.Fly);
 			var angle = unit.Facing / 128f * Math.PI;
+			var aircraft = self.traits.Get<Aircraft>();
 
 			self.CenterLocation += speed * -float2.FromAngle((float)angle);
-			self.Location = ((1 / 24f) * self.CenterLocation).ToInt2();
+			aircraft.Location = ((1 / 24f) * self.CenterLocation).ToInt2();
 
 			unit.Altitude += Math.Sign(desiredAltitude - unit.Altitude);
 		}
diff --git a/OpenRA.Mods.RA/Activities/HeliAttack.cs b/OpenRA.Mods.RA/Activities/HeliAttack.cs
index fae9b230ed..1d4edcfec3 100644
--- a/OpenRA.Mods.RA/Activities/HeliAttack.cs
+++ b/OpenRA.Mods.RA/Activities/HeliAttack.cs
@@ -44,6 +44,7 @@ namespace OpenRA.Mods.RA.Activities
 				return NextActivity;
 			}
 			var unit = self.traits.Get<Unit>();
+			var aircraft = self.traits.Get<Aircraft>();
 
 			var info = self.Info.Traits.Get<HelicopterInfo>();
 			if (unit.Altitude != info.CruiseAltitude)
@@ -62,7 +63,7 @@ namespace OpenRA.Mods.RA.Activities
 
 			if (!float2.WithinEpsilon(float2.Zero, dist, range * Game.CellSize))
 				self.CenterLocation += (rawSpeed / dist.Length) * dist;
-
+
 			return this;
 		}
 
diff --git a/OpenRA.Mods.RA/Activities/HeliFly.cs b/OpenRA.Mods.RA/Activities/HeliFly.cs
index 533cb24b96..ceede06670 100644
--- a/OpenRA.Mods.RA/Activities/HeliFly.cs
+++ b/OpenRA.Mods.RA/Activities/HeliFly.cs
@@ -43,6 +43,7 @@ namespace OpenRA.Mods.RA.Activities
 
 			var unit = self.traits.Get<Unit>();
 			var info = self.Info.Traits.Get<HelicopterInfo>();
+			var aircraft = self.traits.Get<Aircraft>();
 
 			if (unit.Altitude != info.CruiseAltitude)
 			{
@@ -54,7 +55,7 @@ namespace OpenRA.Mods.RA.Activities
 			if (float2.WithinEpsilon(float2.Zero, dist, 2))
 			{
 				self.CenterLocation = Dest;
-				self.Location = ((1 / 24f) * self.CenterLocation).ToInt2();
+				aircraft.Location = ((1 / 24f) * self.CenterLocation).ToInt2();
 				return NextActivity;
 			}
 
@@ -64,7 +65,7 @@ namespace OpenRA.Mods.RA.Activities
 
 			var rawSpeed = .2f * Util.GetEffectiveSpeed(self, UnitMovementType.Fly);
 			self.CenterLocation += (rawSpeed / dist.Length) * dist;
-			self.Location = ((1 / 24f) * self.CenterLocation).ToInt2();
+			aircraft.Location = ((1 / 24f) * self.CenterLocation).ToInt2();
 
 			return this;
 		}
diff --git a/OpenRA.Mods.RA/Activities/Land.cs b/OpenRA.Mods.RA/Activities/Land.cs
index 49f9e117cb..4e64474f01 100644
--- a/OpenRA.Mods.RA/Activities/Land.cs
+++ b/OpenRA.Mods.RA/Activities/Land.cs
@@ -50,6 +50,7 @@ namespace OpenRA.Mods.RA.Activities
 				return NextActivity;
 
 			var unit = self.traits.Get<Unit>();
+			var aircraft = self.traits.Get<Aircraft>();
 
 			if (unit.Altitude > 0)
 				--unit.Altitude;
@@ -60,7 +61,7 @@ namespace OpenRA.Mods.RA.Activities
 			var angle = unit.Facing / 128f * Math.PI;
 
 			self.CenterLocation += speed * -float2.FromAngle((float)angle);
-			self.Location = ((1 / 24f) * self.CenterLocation).ToInt2();
+			aircraft.Location = ((1 / 24f) * self.CenterLocation).ToInt2();
 
 			return this;
 		}
diff --git a/OpenRA.Mods.RA/Aircraft.cs b/OpenRA.Mods.RA/Aircraft.cs
new file mode 100755
index 0000000000..6d06c5f45a
--- /dev/null
+++ b/OpenRA.Mods.RA/Aircraft.cs
@@ -0,0 +1,68 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007,2009,2010 Chris Forbes, Robert Pepperell, Matthew Bowra-Dean, Paul Chote, Alli Witheford.
+ * This file is part of OpenRA.
+ * 
+ *  OpenRA is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ * 
+ *  OpenRA is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ * 
+ *  You should have received a copy of the GNU General Public License
+ *  along with OpenRA.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using OpenRA.GameRules;
+
+namespace OpenRA.Traits
+{
+	public class AircraftInfo : ITraitInfo
+	{
+		public readonly int CruiseAltitude = 20;
+		public readonly string[] RepairBuildings = { "fix" };
+		public readonly string[] RearmBuildings = { "hpad", "afld" };
+
+		public virtual object Create( ActorInitializer init ) { return new Aircraft( init ); }
+	}
+
+	public class Aircraft : IOccupySpace, IMovement
+	{
+		[Sync]
+		public int2 Location;
+
+		public Aircraft( ActorInitializer init )
+		{
+			this.Location = init.location;
+		}
+
+		public int2 TopLeft
+		{
+			get { return Location; }
+		}
+
+		public IEnumerable<int2> OccupiedCells()
+		{
+			// TODO: make helis on the ground occupy a space.
+			yield break;
+		}
+
+		public bool AircraftCanEnter(Actor self, Actor a)
+		{
+			var aircraft = self.Info.Traits.Get<AircraftInfo>();
+			return aircraft.RearmBuildings.Contains( a.Info.Name )
+				|| aircraft.RepairBuildings.Contains( a.Info.Name );
+		}
+
+		public UnitMovementType GetMovementType() { return UnitMovementType.Fly; }
+		public bool CanEnterCell(int2 location) { return true; }
+	}
+}
diff --git a/OpenRA.Mods.RA/Crate.cs b/OpenRA.Mods.RA/Crate.cs
index de39f8eb03..99e24922a6 100644
--- a/OpenRA.Mods.RA/Crate.cs
+++ b/OpenRA.Mods.RA/Crate.cs
@@ -42,16 +42,21 @@ namespace OpenRA.Mods.RA
 	class CrateInfo : ITraitInfo, ITraitPrerequisite<RenderSimpleInfo>
 	{
 		public readonly int Lifetime = 5; // Seconds
-		public object Create(ActorInitializer init) { return new Crate(init.self); }
+		public object Create(ActorInitializer init) { return new Crate(init); }
 	}
 
 	class Crate : ICrushable, IOccupySpace, ITick
 	{
 		readonly Actor self;
+		[Sync]
+		readonly int2 location;
+		[Sync]
 		int ticks;
-		public Crate(Actor self)
+
+		public Crate(ActorInitializer init)
 		{
-			this.self = self;
+			this.self = init.self;
+			this.location = init.location;
 			self.World.WorldActor.traits.Get<UnitInfluence>().Add(self, this);
 		}
 
@@ -75,7 +80,9 @@ namespace OpenRA.Mods.RA
 		public bool IsPathableCrush(UnitMovementType umt, Player player) { return true; }
 		public bool IsCrushableBy(UnitMovementType umt, Player player) { return true; }
 
-		public IEnumerable<int2> OccupiedCells() { yield return self.Location; }
+		public int2 TopLeft { get { return location; } }
+
+		public IEnumerable<int2> OccupiedCells() { yield return TopLeft; }
 		
 		public void Tick(Actor self)
 		{
diff --git a/OpenRA.Mods.RA/Effects/Parachute.cs b/OpenRA.Mods.RA/Effects/Parachute.cs
index 85de93c4b6..d27905f41e 100644
--- a/OpenRA.Mods.RA/Effects/Parachute.cs
+++ b/OpenRA.Mods.RA/Effects/Parachute.cs
@@ -71,7 +71,6 @@ namespace OpenRA.Mods.RA.Effects
 							cargo.traits.Get<Mobile>().TeleportTo(cargo, loc);
 						else
 						{
-							cargo.Location = loc;
 							cargo.CenterLocation = Traits.Util.CenterOfCell(loc);
 
 							if (cargo.traits.Contains<IOccupySpace>())
diff --git a/OpenRA.Mods.RA/Helicopter.cs b/OpenRA.Mods.RA/Helicopter.cs
index d44b3c3092..2f4883c821 100644
--- a/OpenRA.Mods.RA/Helicopter.cs
+++ b/OpenRA.Mods.RA/Helicopter.cs
@@ -27,28 +27,19 @@ using OpenRA.Mods.RA.Activities;
 
 namespace OpenRA.Mods.RA
 {
-	class HelicopterInfo : ITraitInfo
+	class HelicopterInfo : AircraftInfo
 	{
-		public readonly string[] RepairBuildings = { "fix" };
-		public readonly string[] RearmBuildings = { "hpad" };
-		public readonly int CruiseAltitude = 20;
 		public readonly int IdealSeparation = 40;
 		public readonly bool LandWhenIdle = true;
 
-		public object Create(ActorInitializer init) { return new Helicopter(init.self); }
+		public override object Create( ActorInitializer init ) { return new Helicopter( init ); }
 	}
-
-	class Helicopter : ITick, IIssueOrder, IResolveOrder, IMovement
+
+	class Helicopter : Aircraft, IIssueOrder, IResolveOrder
 	{
 		public IDisposable reservation;
-		public Helicopter(Actor self) {}
 
-		static bool HeliCanEnter(Actor self, Actor a)
-		{
-			if (self.Info.Traits.Get<HelicopterInfo>().RearmBuildings.Contains(a.Info.Name)) return true;
-			if (self.Info.Traits.Get<HelicopterInfo>().RepairBuildings.Contains(a.Info.Name)) return true;
-			return false;
-		}
+		public Helicopter( ActorInitializer init ) : base( init ) { }
 
 		public Order IssueOrder(Actor self, int2 xy, MouseInput mi, Actor underCursor)
 		{
@@ -60,7 +51,7 @@ namespace OpenRA.Mods.RA
 					return new Order("Move", self, xy);
 			}
 
-			if (HeliCanEnter(self, underCursor)
+			if (AircraftCanEnter(self, underCursor)
 				&& underCursor.Owner == self.Owner
 				&& !Reservable.IsReserved(underCursor))
 				return new Order("Enter", self, underCursor);
@@ -113,13 +104,13 @@ namespace OpenRA.Mods.RA
 			var rawSpeed = .2f * Util.GetEffectiveSpeed(self, UnitMovementType.Fly);
 			var otherHelis = self.World.FindUnitsInCircle(self.CenterLocation, self.Info.Traits.Get<HelicopterInfo>().IdealSeparation)
 				.Where(a => a.traits.Contains<Helicopter>());
-
+
 			var f = otherHelis
 				.Select(h => self.traits.Get<Helicopter>().GetRepulseForce(self, h))
 				.Aggregate(float2.Zero, (a, b) => a + b);
 
 			self.CenterLocation += rawSpeed * f;
-			self.Location = ((1 / 24f) * self.CenterLocation).ToInt2();
+			Location = ((1 / 24f) * self.CenterLocation).ToInt2();
 		}
 			
 		const float Epsilon = .5f;
@@ -135,9 +126,6 @@ namespace OpenRA.Mods.RA
 			if (d.LengthSquared < Epsilon)
 				return float2.FromAngle((float)self.World.SharedRandom.NextDouble() * 3.14f);
 			return (5 / d.LengthSquared) * d;
-		}
-		
-		public UnitMovementType GetMovementType() { return UnitMovementType.Fly; }
-		public bool CanEnterCell(int2 location) { return true; }
+		}
 	}
 }
diff --git a/OpenRA.Mods.RA/Husk.cs b/OpenRA.Mods.RA/Husk.cs
index d3ab58c686..a867399b97 100644
--- a/OpenRA.Mods.RA/Husk.cs
+++ b/OpenRA.Mods.RA/Husk.cs
@@ -8,18 +8,24 @@ namespace OpenRA.Mods.RA
 {
 	class HuskInfo : ITraitInfo
 	{
-		public object Create( ActorInitializer init ) { return new Husk( init.self ); }
+		public object Create( ActorInitializer init ) { return new Husk( init ); }
 	}
 
 	class Husk : IOccupySpace
 	{
 		Actor self;
-		public Husk(Actor self) 
+		[Sync]
+		int2 location;
+
+		public Husk(ActorInitializer init)
 		{
-			this.self = self;
+			this.self = init.self;
+			this.location = init.location;
 			self.World.WorldActor.traits.Get<UnitInfluence>().Add(self, this);
 		}
 
-		public IEnumerable<int2> OccupiedCells() { yield return self.Location; }
+		public int2 TopLeft { get { return location; } }
+
+		public IEnumerable<int2> OccupiedCells() { yield return TopLeft; }
 	}
 }
diff --git a/OpenRA.Mods.RA/Mine.cs b/OpenRA.Mods.RA/Mine.cs
index bd3b43b11c..6e3951cdb3 100644
--- a/OpenRA.Mods.RA/Mine.cs
+++ b/OpenRA.Mods.RA/Mine.cs
@@ -32,15 +32,19 @@ namespace OpenRA.Mods.RA
 		public readonly string Weapon = "ATMine";
 		public readonly bool AvoidFriendly = true;
 
-		public object Create(ActorInitializer init) { return new Mine(init.self); }
+		public object Create(ActorInitializer init) { return new Mine(init); }
 	}
 
 	class Mine : ICrushable, IOccupySpace
 	{
 		readonly Actor self;
-		public Mine(Actor self)
+		[Sync]
+		readonly int2 location;
+
+		public Mine(ActorInitializer init)
 		{
-			this.self = self;
+			this.self = init.self;
+			this.location = init.location;
 			self.World.WorldActor.traits.Get<UnitInfluence>().Add(self, this);
 		}
 
@@ -64,7 +68,9 @@ namespace OpenRA.Mods.RA
 			return self.Info.Traits.Get<MineInfo>().TriggeredBy.Contains(umt);
 		}
 
-		public IEnumerable<int2> OccupiedCells() { yield return self.Location; }
+		public int2 TopLeft { get { return location; } }
+
+		public IEnumerable<int2> OccupiedCells() { yield return TopLeft; }
 	}
 
 	/* tag trait for stuff that shouldnt trigger mines */
diff --git a/OpenRA.Mods.RA/OpenRA.Mods.RA.csproj b/OpenRA.Mods.RA/OpenRA.Mods.RA.csproj
index 936581e439..6d73bc7a2c 100644
--- a/OpenRA.Mods.RA/OpenRA.Mods.RA.csproj
+++ b/OpenRA.Mods.RA/OpenRA.Mods.RA.csproj
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project ToolsVersion="3.5" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
@@ -69,6 +69,7 @@
     <Compile Include="Activities\Teleport.cs" />
     <Compile Include="Activities\UnloadCargo.cs" />
     <Compile Include="Activities\Wait.cs" />
+    <Compile Include="Aircraft.cs" />
     <Compile Include="AirstrikePower.cs" />
     <Compile Include="AttackFrontal.cs" />
     <Compile Include="AttackHeli.cs" />
diff --git a/OpenRA.Mods.RA/OreRefinery.cs b/OpenRA.Mods.RA/OreRefinery.cs
index 509d8e7ab7..781cf34796 100755
--- a/OpenRA.Mods.RA/OreRefinery.cs
+++ b/OpenRA.Mods.RA/OreRefinery.cs
@@ -41,7 +41,7 @@ namespace OpenRA.Mods.RA
 		public object Create(ActorInitializer init) { return new OreRefinery(init.self, this); }
 	}
 
-	class OreRefinery : ITick, IAcceptOre, INotifyDamage, INotifySold, INotifyCapture, IPips, ITraitPrerequisite<IAcceptOreDockAction>
+	class OreRefinery : ITick, IAcceptOre, INotifyDamage, INotifySold, INotifyCapture, IPips
 	{
 		readonly Actor self;
 		readonly OreRefineryInfo Info;
diff --git a/OpenRA.Mods.RA/Plane.cs b/OpenRA.Mods.RA/Plane.cs
index 2c5d3030df..7dbcd08996 100644
--- a/OpenRA.Mods.RA/Plane.cs
+++ b/OpenRA.Mods.RA/Plane.cs
@@ -27,23 +27,16 @@ using OpenRA.Mods.RA.Activities;
 
 namespace OpenRA.Mods.RA
 {
-	public class PlaneInfo : TraitInfo<Plane>
+	public class PlaneInfo : AircraftInfo
 	{
-		public readonly int CruiseAltitude = 20;
-		public readonly string[] RearmBuildings = { "afld" };
-		public readonly string[] RepairBuildings = { "fix" };
+		public override object Create( ActorInitializer init ) { return new Plane( init ); }
 	}
 
-	public class Plane : IIssueOrder, IResolveOrder, IMovement
+	public class Plane : Aircraft, IIssueOrder, IResolveOrder
 	{
 		public IDisposable reservation;
 
-		static bool PlaneCanEnter(Actor self, Actor a)
-		{
-			var plane = self.Info.Traits.Get<PlaneInfo>();
-			return plane.RearmBuildings.Contains(a.Info.Name) 
-				|| plane.RepairBuildings.Contains(a.Info.Name);
-		}
+		public Plane( ActorInitializer init ) : base( init ) { }
 
 		public Order IssueOrder(Actor self, int2 xy, MouseInput mi, Actor underCursor)
 		{
@@ -52,7 +45,7 @@ namespace OpenRA.Mods.RA
 			if (underCursor == null)
 				return new Order("Move", self, xy);
 
-			if (PlaneCanEnter(self, underCursor)
+			if (AircraftCanEnter(self, underCursor)
 				&& underCursor.Owner == self.Owner
 				&& !Reservable.IsReserved(underCursor))
 				return new Order("Enter", self, underCursor);
@@ -90,8 +83,5 @@ namespace OpenRA.Mods.RA
 						? (IActivity)new Rearm() : new Repair(order.TargetActor));
 			}
 		}
-
-		public UnitMovementType GetMovementType() { return UnitMovementType.Fly; }
-		public bool CanEnterCell(int2 location) { return true; }
 	}
 }
diff --git a/OpenRA.Mods.RA/RenderBuildingWall.cs b/OpenRA.Mods.RA/RenderBuildingWall.cs
index 295bce182a..ae4c59ab87 100644
--- a/OpenRA.Mods.RA/RenderBuildingWall.cs
+++ b/OpenRA.Mods.RA/RenderBuildingWall.cs
@@ -110,19 +110,19 @@ namespace OpenRA.Mods.RA
 
 				foreach (var w in adjWalls)
 				{
-					w.traits.Get<RenderBuildingWall>().AddAdjacentWall(w, self);
-					AddAdjacentWall(self, w);
+					w.traits.Get<RenderBuildingWall>().AddAdjacentWall(w.Location, self.Location);
+					AddAdjacentWall(self.Location, w.Location);
 				}
 				hasTicked = true;
 			}
 		}
 
-		void AddAdjacentWall(Actor self, Actor other)
+		void AddAdjacentWall(int2 location, int2 otherLocation)
 		{
-			if (other.Location == self.Location + new int2(0, -1)) adjacentWalls |= 1;
-			if (other.Location == self.Location + new int2(+1, 0)) adjacentWalls |= 2;
-			if (other.Location == self.Location + new int2(0, +1)) adjacentWalls |= 4;
-			if (other.Location == self.Location + new int2(-1, 0)) adjacentWalls |= 8;
+			if (otherLocation == location + new int2(0, -1)) adjacentWalls |= 1;
+			if (otherLocation == location + new int2(+1, 0)) adjacentWalls |= 2;
+			if (otherLocation == location + new int2(0, +1)) adjacentWalls |= 4;
+			if (otherLocation == location + new int2(-1, 0)) adjacentWalls |= 8;
 		}
 	}
 }
diff --git a/OpenRA.Mods.RA/SpyPlanePower.cs b/OpenRA.Mods.RA/SpyPlanePower.cs
index 732edf68a7..9d7e5e04a8 100644
--- a/OpenRA.Mods.RA/SpyPlanePower.cs
+++ b/OpenRA.Mods.RA/SpyPlanePower.cs
@@ -64,7 +64,6 @@ namespace OpenRA.Mods.RA
 				plane.QueueActivity(new Fly(Util.CenterOfCell(order.TargetLocation)));
 				plane.QueueActivity(new CallFunc(() => plane.World.AddFrameEndTask( w => 
 					{
-						
 						var camera = w.CreateActor("camera", order.TargetLocation, Owner);
 						camera.QueueActivity(new Wait((int)(25 * 60 * (Info as SpyPlanePowerInfo).RevealTime)));
 						camera.QueueActivity(new RemoveSelf());
diff --git a/OpenRA.Mods.RA/Wall.cs b/OpenRA.Mods.RA/Wall.cs
index d59c07cbef..a85a08b7b3 100644
--- a/OpenRA.Mods.RA/Wall.cs
+++ b/OpenRA.Mods.RA/Wall.cs
@@ -32,17 +32,16 @@ namespace OpenRA.Mods.RA
 		public object Create(ActorInitializer init) { return new Wall(init.self); }
 	}
 
-	public class Wall : ICrushable, IOccupySpace, IBlocksBullets
+	public class Wall : ICrushable, IBlocksBullets
 	{
 		readonly Actor self;
+
 		public Wall(Actor self)
 		{
 			this.self = self;
-			self.World.WorldActor.traits.Get<UnitInfluence>().Add(self, this);
+			self.World.WorldActor.traits.Get<UnitInfluence>().Add(self, self.traits.Get<Building>());
 		}
 
-		public IEnumerable<int2> OccupiedCells() { yield return self.Location; }
-
 		public void OnCrush(Actor crusher) { self.InflictDamage(crusher, self.Health, null); }
 		public bool IsCrushableBy(UnitMovementType umt, Player player)
 		{
diff --git a/mods/ra/defaults.yaml b/mods/ra/defaults.yaml
index 620090a772..310595fc12 100644
--- a/mods/ra/defaults.yaml
+++ b/mods/ra/defaults.yaml
@@ -110,4 +110,4 @@
 		Priority: -1
 	HiddenUnderFog:
 	RevealsShroud:
-	Burns:
\ No newline at end of file
+	Burns:
diff --git a/mods/ra/system.yaml b/mods/ra/system.yaml
index 0be779e6aa..b075758125 100644
--- a/mods/ra/system.yaml
+++ b/mods/ra/system.yaml
@@ -345,6 +345,7 @@ CRATE:
 	BelowUnits:
 
 CAMERA:
+	Aircraft:
 	Unit:
 		HP:1000
 		Sight: 10
diff --git a/mods/ra/vehicles.yaml b/mods/ra/vehicles.yaml
index 3c1eaed7e5..ebb5102caf 100644
--- a/mods/ra/vehicles.yaml
+++ b/mods/ra/vehicles.yaml
@@ -543,6 +543,7 @@ MIG:
 		PrimaryWeapon: Maverick
 		SecondaryWeapon: Maverick
 	Plane:
+		RearmBuildings: afld
 	RenderUnit:
 	WithShadow:
 	LimitedAmmo:
@@ -572,6 +573,7 @@ YAK:
 		PrimaryWeapon: ChainGun
 		SecondaryWeapon: ChainGun
 	Plane:
+		RearmBuildings: afld
 	RenderUnit:
 	WithShadow:
 	LimitedAmmo:
@@ -597,6 +599,7 @@ TRAN:
 		Sight: 12
 		Speed: 12
 	Helicopter:
+		RearmBuildings: hpad
 	RenderUnitRotor:
 		PrimaryOffset: 0,14,0,-4
 		SecondaryOffset: 0,-14,0,-2
@@ -630,6 +633,7 @@ HELI:
 		PrimaryOffset: -5,0,0,2
 		SecondaryOffset: 5,0,0,2
 	Helicopter:
+		RearmBuildings: hpad
 	RenderUnitRotor:
 		PrimaryOffset: 0,0,0,-2
 	WithShadow:
@@ -660,6 +664,7 @@ HIND:
 		PrimaryOffset: -5,0,0,2
 		SecondaryOffset: 5,0,0,2
 	Helicopter:
+		RearmBuildings: hpad
 	RenderUnitRotor:
 	WithShadow:
 	LimitedAmmo: